Objectives: This study aimed to investigate the level of problem-solving skills in 1-4 year-old children with early treated phenylketonuria (ETPKU).

Methods:This analytic, cross-sectional study was conducted on 70 1-4 year-old children referred to phenylketonuria (PKU) clinics that had been diagnosed on screening at birth and had been treated. The measurements were a demographic questionnaire, Ages & Stages Questionnaire (ASQ) and clinical assessment by a pediatrician. One hundred children were also selected randomly from Tehran’s kindergartens as the control group, who also completed the above questionnaires. Data were analyzed by SPSS 19.0 software.

Results: The mean age of the children was 29.71 months in the control group and 28.51 months in the case group. There were no significant differences between the two groups regarding the type of delivery and the current and birth heights, weights and headcircumferences. There was a significant difference between the two groups regarding problem-solving developmental skills (P<0.000). The level of problem-solving developmental skills in the children with ETPKU was lower than normal children.

Discussion: It seems that Iranian children with ETPKU, regardless of being on a diet, have lower problem-solving skills. It is recommended to revise their diet and treatment and also to plan programs for early detection, and to carry out interventions for developmental delays in these children.